Implications of Temperature Abuse on Unpasteurized Beer Quality Using Organoleptic and Chemical Analyses

foods Article Implications of Temperature Abuse on Unpasteurized Beer Quality Using Organoleptic and Chemical Analyses Zahra H. Mohammad , Christopher C. Ray, Jack A. Neal, Glenn Cordua, Aaron Corsi and Sujata A. Sirsat * Conrad N. Hilton College of Hotel and Restaurant Management, University of Houston, Houston, TX 77204-3028, USA; [email protected] (Z.H.M.); [email protected] (C.C.R.); [email protected] (J.A.N.); [email protected] (G.C.); [email protected] (A.C.) * Correspondence: [email protected]; Tel.: +1-713-743-2624 Received: 29 June 2020; Accepted: 29 July 2020; Published: 1 August 2020 Abstract: Beer flavor and sensory quality are affected by storage time and temperature due to chemical breakdown and aging. This study aimed to investigate the organoleptic properties of temperature-abused, unpasteurized craft beer and analyze the chemical breakdown associated with the process. Sensory tests were performed using a triangle test to determine consumer identification of temperature-abused beer. The chemical tests were conducted to determine the chemical breakdown of the two beer groups: control beer (COB) and temperature-abused beer (TAB). The chemical analysis of the two beer groups showed significant changes in multiple chemical compounds such as ethyl esters, linear aldehydes, and sulphur-compounds; however, the sensory analysis results were not significant even though 39% of participants were able to detect differences. in this study, two factors identified that caused chemical reactions in the TABs were oxidation and live yeast cells. In conclusion, these results can be used by beer producers to ensure a quality product throughout the distribution chain by controlling time and temperature. Keywords: unpasteurized beer; sensory evaluation; chemical breakdown; temperature; beer quality 1. Introduction Beer is one of the most popular alcoholic beverages and is consumed in almost every country in the world in vast quantities [1,2]. Beer is a natural product that deteriorates at different rates depending upon the rate of time and temperature exposure [3]. The storage temperature of beer at various stages of the delivery chain affects chemical reactions that control the aging characteristics of the beer [3,4]. From brewery to consumer, commercial beer is exposed to several temperature fluctuations that can alter sensory properties and cause negative aging effects due to the chemical reactions in the beer over time [5,6]. According to Cejkaˇ et al. [3], during beer storage, the following processes occur: formation of stale flavors, haze and browning, reduction in bitterness, and decrease in fruity aroma. Thus, beer quality gradually decreases with elapsed time in storage. Consumers assess several characteristics of beer to determine the overall quality [7] including sensory or taste [8,9]. Codină et al. [9] conducted a sensory analysis on Romanian beers and found a significant correlation between the sensory attributes and the chemical parameters through physico-chemical parameters that are responsible for the sensorial attributes of beer. Taste and aroma may be perceived separately, but they are often integrated to produce a total flavor impression [10]. Aroma is an important factor that the consumer perceives for assessing the quality of beer [7]. Beer aroma mostly consists of higher alcohols and esters [11]. A change in the concentration of Foods 2020, 9, 1032; doi:10.3390/foods9081032 www.mdpi.com/journal/foods Foods 2020, 9, 1032 2 of 10 these compounds may destroy the balance of the beer aroma [12]. Aroma control is a process where brewers control the possible conditions that can alter the beers aromatic properties during the brewing process. Researchers have isolated the various essential volatile compounds that affect beer flavor [13]. The chemical classes associated with these compounds include linear aldehydes, strecker aldehydes, ketones, cyclic acetyls, heterocyclic compounds, ethyl esters, lactones, and s-compounds. These chemical classes contain the most common chemical compounds found in beer that affects quality and flavor [13]. However, the volatile compounds profile of the beer is influenced by the yeast strain used for beer fermentation [14]. Marconi et al. [14] conducted two different experimental conditions where beer samples were either stored at 20 or 30 ◦C to investigate the influence of yeast strain, priming solution, and temperature on beer quality. The researchers also investigated the standard quality attributes, volatile compounds, and sensory profile of the bottle-conditioned beer. The authors found that the volatile profile was affected by the strain of yeast due to varied metabolic activity for each yeast strain. The authors also found that the Safbrew S-33® yeast strain, when primed with Siromix® and refermented at 30 ◦C, yielded the fastest formation of higher alcohols while maintaining low production of off-flavors. Finally, the authors concluded that a formulation of two yeast strains might reduce the time needed for bottle conditioning without affecting the quality of the final beer and improve efficiency and economic profits [14]. The oxidation of bitter beer acids and oxidation and polymerization of malt and hop polyphenols could also occur during beer storage [15]. These unwanted reactions also cause adverse effects on TAB during storage conditions. Oxygen can affect beer during storage by contributing to its deterioration and shortening the shelf life [12]. Oxygen deteriorates final packaged beer by altering appearance, color, taste, aroma, and most importantly, beer flavor [12]. In modern bottle filling equipment in the breweries is designed to achieve very low levels (0.03 mg/L) of O2 concentrations. Even with the low-level oxygen content of the final package beer bottles, there is still enough oxygen to formulate staling substances [16]. Few academic studies have been conducted to determine the effect of time-temperature abuse and agitation on the quality of beer. The primary focus of the previous literature to date regarding beer quality has been to determine the chemical deterioration that occurs in general and substandard storage conditions. In addition, the majority of craft beers are non-pasteurized. Currently, the predominant quality problem of beer can be attributed to the change in its chemical composition during storage, which may alter the sensory properties [5,13]. The overall objective of this study was to determine the effect of temperature abuse on the chemical breakdown, sensory properties of unpasteurized bottled beer, and the implications for the industry and manufactures. 2. Materials and Methods The approach of this study is based on quasi-experimental design. According to Shadish and Galindo [17], a quasi-experimental design manipulates treatments to determine their effects. This design approach differs from randomized experiments in that units are not randomly assigned to conditions. The quasi-experimental design combined the multiple measurements of the chemical analysis along with the sensory analysis of the two time/temperature variations in the beer to determine the consumer awareness of TAB. The dependent variable in this study was the chemical breakdown of TAB. The chemical compounds were isolated and identified from the sampled beer resulting from the temperature abuse. The chemical breakdown was dependent on the two independent variables: storage time and temperature. 2.1. Beer Preparation A Kölsch style bottled beer was used for this study. This type of beer was selected due to the assessment performed by Vanderhaegen et al. [18], who reported that lighter style beers represent the largest part of the beer market. The particular light style beer brand selected for this study was Foods 2020, 9, 1032 3 of 10 not pasteurized during the production process. The pasteurization process aids in the elimination of micro-organisms, which may cause spoilage in beer. Thus, the use of unpasteurized bottled beer may increase the likelihood of identifying volatile compounds. As of December 2019, according to the Institute for Brewing Studies, there are now nearly 4522 microbreweries and 2594 brewpubs that produce 1,180,393 barrels of craft beer in Texas. In Texas, the number of craft breweries reached 341 in 2019 based on Brewers Association. Due to this growing segment in the beer industry, the researchers selected a local Texan craft microbrewery. The vast majority of craft beers are non-pasteurized [19]. The beer bottles were obtained directly off of the bottling line to avoid any prior time/temperature variations that might alter the data. (Table1) presents the two manipulated time/temperature variations used in this study: Group A was the control (COB) group and was stored at the ideal conditions for storage at 3 ◦C for 35 days based on the Brewers Association [20]. Group A beer was stored in a Beverage Air Piedmont Line (PR24-1A, Spartenburg) refrigerator. This simulated group beer has been kept cold from the brewery to end consumer. Group B beer was stored at 35 ◦C for 30 days in an incubator (Fisher Scientific Isotemp Model 637D, Kansas City) and then stored at 3 ◦C for five days in a Beverage Air Piedmont Line refrigerator before sensory analysis. This transfer simulates retail or on-premise outlets that purchase the beer and then cool it before serving the consumer. The temperature of 35 ◦C simulates the storage temperature of non-refrigerated warehouses where beer is stored before being shipped to the various retail outlets for purchase by consumers and was chosen based on the results of Corzo and Brancho [21]. Table 1. Beer Group Time/Temperature Treatment *. Beer Group Temperature Time (Days) A 3 C( 0.5 C) 35 ◦ ± ◦ B 35 C( 0.2 C) 30 ◦ ± ◦ B 3 C( 0.5 C) 5 ◦ ± ◦ * All beer served at 3 ◦C during sensory analysis. 2.2. Chemical Analysis After the two beer groups were exposed to temperature treatments for the specific time, they were packaged and shipped to Siebel Institute to conduct the chemical analysis in White Labs Analytical Services division in San Diego. Beer Groups A and B were packaged in an insulated container, packed with dry ice and expressed shipped overnight.

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